06/2024 (part 1)

Author: breadadams

2024/06/index.ts

@@ -0,0 +1,94 @@
+import { getPuzzle } from "../../utils";
+
+const puzzleInput = getPuzzle(__dirname).trim();
+
+const map = puzzleInput.split("\n").map((row) => row.split(""));
+const GUARD_STARTING_CHAR = "^";
+const OBSTACLE_CHAR = "#";
+const DIRECTIONS = {
+  UP: { x: 0, y: -1 },
+  RIGHT: { x: 1, y: 0 },
+  DOWN: { x: 0, y: 1 },
+  LEFT: { x: -1, y: 0 },
+} as const;
+
+const DIRECTION_KEYS = Object.keys(DIRECTIONS) as Array<
+  keyof typeof DIRECTIONS
+>;
+
+const MAP_WIDTH = map[0].length;
+const MAP_HEIGHT = map.length;
+
+type GuardPosition = {
+  x: number;
+  y: number;
+  direction: keyof typeof DIRECTIONS;
+};
+
+const startY = map.findIndex((row) => row.includes(GUARD_STARTING_CHAR));
+const startX = map[startY].indexOf(GUARD_STARTING_CHAR);
+
+const getVisitedCells = (
+  mapInput: typeof map,
+  keyFormatter: (guardPos: GuardPosition) => string = ({ x, y }) => `${x},${y}`,
+  enableLoopDetection = false
+) => {
+  let guardPosition: GuardPosition = { x: startX, y: startY, direction: "UP" };
+  let loopDetected = false;
+
+  const visitedCells = new Set<string>();
+  visitedCells.add(keyFormatter(guardPosition));
+
+  while (true) {
+    const nextMove = DIRECTIONS[guardPosition.direction];
+    const nextPosition = {
+      x: Math.abs(guardPosition.x + nextMove.x),
+      y: Math.abs(guardPosition.y + nextMove.y),
+    };
+
+    if (
+      nextPosition.x < 0 ||
+      nextPosition.x >= MAP_WIDTH ||
+      nextPosition.y < 0 ||
+      nextPosition.y >= MAP_HEIGHT
+    ) {
+      break;
+    }
+
+    const nextCell = mapInput[nextPosition.y][nextPosition.x];
+
+    if (nextCell === OBSTACLE_CHAR) {
+      const nextDirection =
+        DIRECTION_KEYS[
+          (DIRECTION_KEYS.indexOf(guardPosition.direction) + 1) %
+            DIRECTION_KEYS.length
+        ];
+
+      guardPosition.direction = nextDirection;
+      continue;
+    }
+
+    guardPosition.x = nextPosition.x;
+    guardPosition.y = nextPosition.y;
+    const nextKey = keyFormatter(guardPosition);
+
+    if (enableLoopDetection && visitedCells.has(nextKey)) {
+      loopDetected = true;
+      break;
+    }
+
+    visitedCells.add(nextKey);
+  }
+
+  return { loopDetected, visitedCells };
+};
+
+// Part 1
+(() => {
+  console.time("part 1");
+
+  const { visitedCells } = getVisitedCells(map);
+
+  console.log("part 1 visitedCells count ::", visitedCells.size);
+  console.timeEnd("part 1");
+})();

README.md

@@ -6,6 +6,7 @@
 
 |                    Day                    | Part 1 | Part 2 |
 | :---------------------------------------: | :----: | :----: |
+| [06](https://adventofcode.com/2024/day/6) |   ✅   |    -   |
 | [05](https://adventofcode.com/2024/day/5) |   ✅   |   ✅   |
 | [04](https://adventofcode.com/2024/day/4) |   ✅   |   ✅   |
 | [03](https://adventofcode.com/2024/day/3) |   ✅   |   ✅   |